Characterizing combustion of a hybrid rocket using laser absorption spectroscopy

• Published in: Experimental thermal and fluid science Vol. 127; p. 110411
• Main Authors: Fang, Sihan, Wang, Zezhong, Lin, Xin, Li, Fei, Li, Renjie, Li, Jing, Zhang, Zhedian, Liu, Yan, Yu, Xilong
• Format: Journal Article
• Language: English
• Published: Philadelphia Elsevier Inc 01.09.2021; Elsevier Science Ltd
• Subjects: Absorption spectroscopy; Chemical reactions; Combustion; Combustion efficiency; Computational fluid dynamics; Efficiency; Evaluation; Fluxes; Heat transfer; Hybrid rocket motor; Infrared lasers; Lasers; Mathematical models; Nozzles; Oxidizing agents; Paraffin; Paraffins; Partial pressure; Rocket engines; Rocket firing; Rockets; Semiconductor lasers; Spectrum analysis; Temperature; Tunable diode laser absorption spectroscopy; Tunable lasers; Two dimensional models; Uncertainty; Hybrid rocket motor; Temperature; Partial pressure; Combustion efficiency; Tunable diode laser absorption spectroscopy
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2021.110411

•An optimal H2O line pair near 2.5 mm was selected to construct the TDLAS system.•Variations of temperature and H2O partial pressure were diagnosed.•Combustion efficiency of the hybrid rocket motor was quantitatively evaluated.•Combustion characteristics of the hybrid rocket motor were discussed. The combustion of an oxygen/paraffin hybrid rocket motor was experimentally characterized. Firing tests were conducted for different oxidizer mass fluxes ranging from 2.47 to 3.40 g/ (cm2·s). Variations in temperature and H2O partial pressure at the nozzle exit were diagnosed using mid-infrared tunable diode laser absorption spectroscopy (TDLAS) based on H2O absorption near 2.5 μm. Three H2O absorption lines were simultaneously covered by only one distributed feedback (DFB) laser using scanned-wavelength direct absorption (DA) mode with 2.0 kHz repetition rate. Measurement uncertainty was analyzed in detail considering line-strength uncertainty and Voigt fitting residuals. A two-dimensional (2D) model of the nozzle was constructed using the ANSYS FLUENT CFD software package. The combustion efficiency of the hybrid rocket motor was evaluated from the perspectives of chemical reaction and heat release, respectively, based on TDLAS results and CFD simulations. The effectiveness of the evaluation was validated by comparing its results with characteristic velocity (C*)-based combustion efficiency. Finally, comparisons of combustion efficiencies among different cases show that increasing the oxidizer mass flux or oxidizer-to-fuel ratio improves the combustion efficiency of the hybrid rocket motor under our experimental conditions.